leaky integrator

In article <C7E22q.3uH at murdoch.acc.Virginia.EDU> cp5m at cajal.med.Virginia.EDU (Colin Prepscius) writes:
>Articles by Softky & Koch, 93, and Levine, 91, (and many more) describe
>modeling of neurons by a "leaky integrator", or "integrate and fire model".
>These are essentially capacitive models of neurons, but they all seem to
>include "reset"; after the neuron fires, its input (voltage) is set back to 0
>(or resting potential).
>>My question is: to what extent is this "reset" biologically plausible? It
>seems to me that such a reset is very different from a refractory period.
The "reset" used in integrate and fire models, both leaky and not, is
intended to mimic the effects of repolarization that occurs in neurons
following a spike, mediated by the delayed potassium current. It isn't
meant to model the refractory period specifically, although it does
result in a relative refractory period, simply to return the spike
initiator to a resting state so that it is ready to fire again.
As an example of what you can do with a version of the leaky integrate
and fire with a variable threshold, you may want to see (shameless
plug here):
BR Parnas and ER Lewis, "A Computationally Efficient Spike Initiator
Model that produces a Wide Variety of Neural Responses" in Neural
Systems: Analysis and Modeling, FH Eeckman (ed), Kluwer Academic
Publishers, pp. 67-76, 1993.
--
bruce
(brp at bandit.berkeley.edu)